During semiconductor wafer fabrication, extreme ultraviolet (EUV) light can be utilized in a lithographic process to enable transfer of very small patterns, such as nanometer-scale patterns, from a mask to the semiconductor wafer. In EUV lithography, a pattern formed on a lithographic mask can be transferred to a semiconductor wafer by reflecting EUV light off of portions of a reflective surface from which an absorbing film has been selectively removed. A pellicle can be placed in front of the mask to prevent unwanted particles from reaching the mask surface and, thereby, altering the pattern formed on the mask. However, since EUV light is highly absorbed by all known materials, placing a reticle in front of the mask can significantly reduce EUV light transmittance, which can undesirably reduce throughput of an EUV lithography exposure tool.
In one approach, a lithographic mask is kept in a box having a lid that is closed to protect the mask from particle contamination. After the lithographic mask has been inserted into the EUV lithography exposure tool, the lid on the box can be opened in the vacuum chamber of the exposure tool just before using the mask. After use, the lid on the box can be quickly closed to protect the mask. However, in this approach, the lithographic mask can be contaminated by particles that are generated as a result of materials rubbing when the lid is opened or closed.